Effect of the Dendrimer Generation Used in the Synthesis of Pt-Ru Nanoparticles Supported on Carbon Nanofibers on the Catalytic Activity towards Methanol Oxidation

Abstract

Pt-Ru nanoparticles supported on carbon nanofibers (CNF) were synthesized by the sodium borohydride reduction method, using different generation dendrimers (zero, one, two and three generations). After the synthesis process, these materials were submitted to a heat treatment at 350 • C, in order to clean the nanoparticle surface of organic residues. TEM characterization showed that the Pt-Ru nanoparticles size ranged between 1.9 and 5.5 nm. The use of dendrimers did not totally avoid the formation of aggregates, although monodisperse sizes were observed. The heat treatment produces the desired surface cleaning, although promoted the formation of agglomerates and crystalline Ru oxides. The study of the electrochemical activity towards the methanol oxidation displayed some clues about the influence of both the dendrimer generation and the presence of Ru oxides. Moreover, the apparent activation energy E ap for this reaction was determined. The results showed a beneficial effect of the heat treatment on the methanol oxidation current densities for the materials synthesized with the biggest dendrimers, being the methanol deprotonation and CO ad diffusion the predominant rate determining steps (rds).

Ce(IV) immobilized on halloysite nanotube–functionalized dendrimer (Ce(IV)–G2): A novel and efficient dendritic catalyst for the synthesis of pyrido[3,2‐c]coumarin derivatives

“…The results surprisingly showed that the prepared dendritic catalyst (Ce (IV)-G2) was the most effective catalyst for this reaction, and the respective pyrido[3,2-c]coumarin 4be was obtained in higher yield than those of pure Ce (OTf) 4 , HNT, or even Ce(OTf) 4 coated on HNT (Ce (OTf) 4 @HNT). The three variables, solvent, temperature, and the amount of catalyst were investigated (entries [16][17][18][19][20][21][22][23][24][25][26][27]. The best yield of the product was obtained using 80 mg Ce(IV)-G2 catalyst (containing 0.0028 mmol T A B L E 3 Optimization of reaction conditions for the synthesis of 4 [a] Entry Catalyst (mol%) Solvent (3 ml) Ce(IV), 0.28 mol%) at 130 C under solvent-free conditions (entry 25).…”

“…[20,21] Due to the improvement of the catalytic activity as well as the simplified recyclability of DEMs, heterogenization of DEMs by immobilizing on insoluble supports has gained much interest. [22][23][24][25] During the past years, using organic or inorganic nanotubular materials as support has attracted attention because of their exceptionally large surface area and specific tube-shaped structure with an empty cavity. [26] Halloysite nanotube (HNT), a kind of naturally occurring aluminosilicate nanoclay (Al 2 Si 2 O 5 (OH) 4 Á2H 2 O with 1:1 ratio of Al/Si), [27] has gained great attention because of its widespread applications [28][29][30][31][32][33][34][35] and advantages such as high mechanical and thermal stability, low price, environmental friendliness, biocompatibility, large surface area, resistibility against organic solvents, and ease of reusability.…”

Leveraging Dendrimer Macromolecules for the Encapsulation and Stabilisation of Nano-Sized Ruthenium Catalysts: Evaluation of Catalytic Reaction Kinetics in the Reduction of Pollutants Organic Dyes, Oxidation of Alcohols and Alkenes as Well as Hydrogenation Reactions

“…Of these Ru-based bimetallic DEN catalysts, supported Pt-Ru dendrimer encapsulated/ stabilised nanoparticles appear to have been well investigated, especially in the oxidation of methanol. For example, Calderón et al reported the electro-oxidation of methanol catalysed by carbon-nanofibers (CNF) supported dendrimer stabilised Pt-Ru nanoparticles [94]. Different generations (G0-3) of PAMAM dendrimers were used for the stabilisation of the synthesised supported Pt-Ru bimetallic nanoparticles Leveraging Dendrimer Macromolecules for the Encapsulation and Stabilisation of Nano-Sized... DOI: http://dx.doi.org/10.5772/intechopen.111453 in this case.…”

Synthesis and applications of carbon nanofibers: a review

“…Heat treatment of the catalysts results in an increase in the particle size as well as the formation of crystalline Ru oxides. However, oxide formation increases the intrinsic catalytic activity for methanol oxidation (Calderón et al 2017). Whereas Calderón et al (2016) have synthesized palladium-nickel nanoparticles supported on CNFs by mixing CNFs, Na 2 PdCl 4 , and NiCl 2 in ultrapure water with sonication.…”